1. Field of the Invention
The present invention relates to a magnetic head device used in a state in which a magnetic head is installed on a base plate, and more particularly, to a structure in which a flexible wiring board is used for the wiring for the terminal pads of the magnetic head.
2. Description of the Related Art
With the improvement in recording density and the digitalization of signal recording format, the magnetic head has a trend toward narrowing the track thereof from year to year. As magnetic heads, various MIG (Metal in GAP) type magnetic heads have hitherto been used, each of which has a structure in which a pair of core halves comprising ferrite or ceramic, and constructed by forming thereon metallic magnetic thin films with a superior soft magnetic characteristic, are integrated using a bonding member such as molten glass, with an insulating film interposed between the two core halves.
In recent years, however, in order to make a track narrower than that of the MIG type magnetic head, a thin film magnetic head with a thin film coil has been used as a helical scan type magnetic head for use in a VTR device, a tape storage device or the like.
FIG. 16 shows one construction example of a thin film magnetic head created under such a situation. This thin film magnetic head A has a structure in which core halves 101 and 102 are integrated with a core built-in layer 103 therebetween, and in which a thin film head portion 108 having a thin film portion and a yoke portion is incorporated into the core built-in layer 103 between the core halves 101 and 102. Here, the core half 102 is formed longer than the core half 101, and on the end portion side of the core built-in layer 103 exposed on the side surface of the core half 102, there are provided a coil portion formed within the core built-in layer 103 and terminal pads 117 to 119 connected to the yoke portion.
Also, in the thin film magnetic head A shown in FIG. 16, a medium sliding surface 110 constituted of a slim convex curved surface on which a magnetic medium slides, is formed on the uppermost portions of the core halves 101 and 102. The purpose of forming the medium sliding surface into a convex curved surface in this magnetic head A is to improve the touch between the medium sliding surface and a magnetic tape as a magnetic recording medium.
When the magnetic head A having the configuration shown in FIG. 16 is used as a helical scan type magnetic head, a recess is provided in the peripheral surface of a rotating cylinder, and the magnetic head A is fixed to this recess. Then, the medium sliding surface 110 is disposed on the peripheral surface side of the rotating cylinder so that the medium sliding surface 110 can slide relative to the magnetic tape under the rotation of the rotating cylinder, whereby magnetic recording or reproduction by the magnetic head A can be implemented using the thin film head portion 108 located at the center portion of the medium sliding surface 110. The installation of the magnetic head A on the rotating cylinder is performed by fixing a base material called “base plate” to the recess of the rotating cylinder with installation means such as screws.
FIGS. 17 and 18 are perspective views each showing a state in which the magnetic head A is installed on this type of base plate 120. The base plate 120 is formed of a metallic plate material with an octagonal form in a plan view, and the magnetic head A is fixedly adhered along the base plate 120 at the center of one side end portion on the top surface of the base plate 120. The medium sliding surface 110 side of the magnetic head A is somewhat projected from the end portion of the base plate 120 and fixed. Bonding wires 117a to 119a each formed of a gold line are respectively connected to terminal pads 117 to 119 formed on the side-surface side of the magnetic head A. These bonding wires 117a to 119a are individually routed to the rear surface side of the base plate 120, and are respectively connected to the terminal portions 122 to 124 of a terminal board 121 formed on the rear surface side of the base plate 120.
FIG. 19 is a partially enlarged view showing a rotating cylinder 130 having the base plate 120 on which the magnetic head shown in FIGS. 18 and 19 is installed. The base plate 120 is installed on the recess formed in the outer peripheral portion of a cylindrical rotating cylinder 130, and the medium sliding surface of the magnetic head A can slide relative to a magnetic tape (magnetic recording medium) wound along the peripheral direction of the rotating cylinder 130. The terminal portions 122 to 124 of the terminal board 121 on the rear surface side of the base plate 120 are used as terminals for connecting with the electrical circuitry of electronic components mounted within the rotating cylinder 130.
In the conventional structure shown in FIGS. 16 to 18, the interconnection between the magnetic head A and the terminal board 121 requires connection work by means of bonding wires. Because the magnetic head has been miniaturized from year to year, wire bonding work performed so as to be extended from the surface side to the rear surface side of the base plate 120 with respect to the magnetic head A with a size of e.g., several mm has become extremely complicated work. Therefore, although an automatic machine such as a robot has been employed, the bonding work has not been efficient work in terms of mass-productivity. Also, after performing connection work by wire bonding, a resin layer has been applied to surroundings of the resin layer to cover the surroundings for protecting the bonding wires. However, this work itself is also complicated work, and labor-saving is required for the work.
In order to solve these problems, the present inventor attempted to use a flexible wiring board instead of bonding wires to wire the magnetic head A on the base plate 120.
FIG. 20 is a side view showing a state in which the flexible wiring board is connected to the magnetic head A, and FIG. 21 is a plan view thereof. The flexible wiring board 140 is formed by covering three wiring lines 141 with a thin resin layer 142, and the resin layer 142 comprises a trunk portion 145, a neck portion 146, and a head portion 147. Here, one end portion side of the wiring lines 141 are exposed on one end of the head portion 147, and terminal 117 to 119 are formed on the trunk portion 145.
When the magnetic head is wired using a flexible wiring board 140 instead of bonding wires, it is necessary to fix the head portion 147 of the flexible wiring board 140 to one portion of the surface of the base plate 120, and therefore, the inventor attempted to perform wiring by forming an adhesion layer on the rear surface of the head portion 147, and after adhering one portion of the head portion 147 to one surface side of the base plate 120, and folding back the neck portion 146 from the one surface side to the other surface side of the base plate 120. However, in such an adhesion structure, when attempting to fold back the neck portion 146, one portion of the head portion 147 once adhered to the surface side of the base plate 120 might fall off from the base plate 120 due to the elasticity of the flexible wiring board itself. This causes a problem in reducing the reliability at mass-production.
This type of flexible wiring board 140 is typically produced by injecting resin around a plurality of wiring lines with a predetermined shape, in alignment with one another, and solidifying the resin, thereby forming a thin resin layer 142 for covering the plurality of wiring lines 141. When large amounts of flexible wiring boards 140 are used, the flexible wiring boards 140 in keeping with an intended shape are mass-produced at a mass-production factory in a manner such that large amounts of flexible wiring boards 140 are formed on tape-shaped support members, in alignment with one another, and are carried into the worksite where the magnetic heads are produced together with the tape-shaped support members. Then, the tape-shaped support member is set in a punching device, and the flexible wiring board portions formed on the tape-shaped support members are each aligned with the die hole of the punching device. Thereafter, by punching flexible wiring board portions one after another into an ultimately intended shape using a punch, flexible wiring boards 140 are produced, each of which is to be used in the wiring process of a magnetic head.
However, the flexible wiring board 140 produced by the punching in this manner has had a tendency to cause a portion curled into a round shape under the stress on the cut portion of resin during punching work. In the case where this curled portion occurs at a resin layer portion other than the resin layer portion to be connected to the terminal pads of the magnetic head A, a problem would not particularly occur. However, in the event that the curl portion occurs in the resin layer on the head portion 147 to be directly connected to each of the terminal pads of the magnetic head A, as shown in FIG. 20, there have been risks of causing bad connection, falling-off of ball bonding portions, and/or cracking therein, when the terminal pad portion of the magnetic head A and the wiring end portion located at the curled resin layer portion are to be interconnected by ball bonding.